According to the state of the art, automatic transmissions, in particular for motor vehicles, comprise planetary gear sets that are shifted by means of friction elements or shift elements and are typically connected to a start-up element that is subject to a slip effect and is alternatively provided with a lock-up clutch, such as a hydrodynamic torque converter or a fluid coupling.
Such automatic transmissions are often described in the state of the art and are subject to continuous development and improvement. Such transmissions should feature a sufficient number of forward gears along with at least one reverse gear and a transmission ratio that is very well suited for motor vehicles, with a high overall spread and favorable progressive steps. Furthermore, they should enable a high starting transmission ratio in the forward direction, and contain a direct gear. In addition, automatic transmissions require low construction costs and a small number of shift elements, whereas, upon a sequential shifting operation, only one shift element is to be switched on, and only one shift element is to be switched off.
Such an automatic transmission is known, for example, from DE 10 2009 028 670 A1. It includes four planetary gear sets arranged behind one another, coaxial to the main axis of rotation, and six shift elements for the shifting of at least nine forward transmission gears and one reverse gear.
With the known transmission, a fourth shaft is connected to the sun gear of the first planetary gear set and the sun gear of the second planetary gear set, is attachable to the housing of the transmission through a first brake and is detachably connectable to the drive shaft through a first clutch, whereas the drive shaft is detachably connectable, through a second clutch, to a seventh shaft connected to the ring gear of the second planetary gear set and, through a third clutch, to an eighth shaft, which is connected to the ring gear of the third planetary gear set and the bar of the fourth planetary gear set and is attachable to the housing through a second brake.
Furthermore, with the known transmission, it is provided that the ring gear of the first planetary gear set is connected to a sixth shaft connected to the bar of the second planetary gear set and the ring gear of the fourth planetary gear set, whereas a third shaft is connected to the sun gear of the third planetary gear set and the sun gear of the fourth planetary gear set and is attachable to the housing through a third brake, and whereas the output shaft is connected to the bar of the third planetary gear set. However, in an adverse manner, the transmission in accordance with DE 10 2009 028 670 A1 is not suitable for installation as a front-transverse system.
Furthermore, a multi-speed hybrid transmission emerges from DE 10 2010 010 122 A1, which comprises an input element, an output element, a first, second and third planetary gear set, each of which features a first, second and third element, whereas the gear sets are arranged along a first and second axis, and a first, second and third outer gear set, which are arranged for the transfer of turning moment between the first and second axes, whereas each of the first, second and third outer gear sets includes the first and second meshing outer gears. The known transmission also includes a motor/generator that is functionally connected to the first outer gear of the second outer gear set, along with five turning moment transfer devices for selectively connecting the elements of the planetary gear sets or of the first and second outer gear with each other, with a fixed element, with the input element or other elements of the planetary gear sets, whereas the five turning moment transfer devices are engaged in combinations of three, in order to produce at least eight forward gears and one reverse gear between the input element and output element.
The present invention is based on the task of, starting from a transmission in accordance with DE 10 2009 028 670 A1, specifying a multi-stage transmission that, viewed axially, features a low need for installation space, such that the installation of the transmission and, optionally, a hybridization of the transmission as a front-transverse system is possible.